The present invention relates to a multiaxis connector for forming a spinal implant equipped with connecting rods.
French patent no. 2 731 344 discloses a spinal implant allowing angular orientation of a connecting rod with respect to the bone anchoring elements.
The anchoring element consists of a fixing screw comprising an anchorage part separated from a protruding threaded head, associated with a clamping nut via an intermediate body of polygonal cross section forming a stop.
The anchoring element also comprises a receiving ring which collaborates with the protruding threaded head of the anchorage part and allows the connecting rod to be fitted.
The receiving ring has two branches connected by a connecting zone to form an element that forms a clip. The two branches are pierced with coaxial facing holes designed to have the protruding threaded head of the fixing screw pass through them and to bear against the polygonal stop.
The connecting zone of the two branches of the ring delimits, at right angles to the facing holes, a bore collaborating with a compressible sleeve equipped with a central passage designed to accommodate the connecting rod.
Assembling the sleeve inside the bore of the ring is intended to create a ball-joint connection so that before the nut is tightened onto the protruding threaded head of the fixing screw, the connecting rod can be positioned in a determined angular position.
The spinal implant described hereinabove has certain disadvantages as regards the fitting of the sleeve inside the bore of the ring forming the ball-joint connection for the pivoting of the connecting rod. Specifically, it is found that this assembly does not allow the connecting rod sufficient travel when the spinal implant is being fitted, because said rod butts against the upper and lower outer edges of the bore.
It is these disadvantages that the present invention intends more specifically to remedy.
Specifically, the multiaxis connector for a spinal implant according to the present invention is intended, on the one hand, to be able to pivot in all directions with respect to the vertebral bodies and, on the other hand, to allow large-amplitude pivoting of the connecting rod with respect to said connector.
The multiaxis connector according to the present invention comprises:
a connecting rod, a fixing screw comprising a first threaded part for anchoring it in the bone tissue, an intermediate head with a hexagonal profile and a second threaded part receiving a clamping nut;
a first connecting element pierced with a bore designed to receive the second threaded part of the fixing screw, with another bore, comprising, in its interior part, an annular track of spherical profile, and with a slot passing through the bore to open into the bore at the annular track;
a second connecting element pierced with a bore designed to receive the connecting rod, with a threaded hole collaborating with a binding screw for immobilizing said rod in terms of translation;
and connecting means forming a ball joint which, on the one hand, allow the first and second connecting elements to be coupled to one another in such a way that said elements can pivot one with respect to the other so as to present the connecting rod in determined angular positions and, on the other hand, allow the connecting rod to be offset laterally with respect to the center of pivoting of said elements.
The multiaxis connector according to the present invention comprises a second connecting element provided with connecting means which consist, on one of the exterior faces of said element, of a finger extended by a head with a spherical profile so that said head can collaborate with the spherical track of the bore of the first connecting element.
The multiaxis connector according to the present invention comprises a first element, the bore of which has cylindrical bearing surfaces on which the clamping nut and the intermediate stop of the fixing screw respectively bear when the connecting means are immobilized in terms of rotation by the tightening of said nut.
The multiaxis connector according to the present invention comprises a first connecting element which, on each side of the slot, has branches joined together by a curved wall, said branches being able to deform under the clamping force of the nut of the fixing screw to immobilize the connecting means in terms of rotation.
The multiaxis connector according to the present invention comprises a first connecting element, the slot of which is arranged in a plane which intersects the main axes of the bores at right angles.
The multiaxis connector according to the present invention comprises a second connecting element, the threaded hole of which opens into the bore in a perpendicular direction.
The description which will follow with reference to the appended drawings, given by way of nonlimiting example, will allow better understanding of the invention, of the characteristics that it has and of the advantages it is likely to afford.